Raised bogs

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Description (English)

The mire surface and underlying peat of highly oligotrophic, strongly acidic peatlands with a raised centre from which water drains towards the edges. The peat is composed mainly of sphagnum remains. Raised bogs form on nearly flat ground and derive moisture and nutrients only from rainfall (ombrotrophic). Raised bog complexes (X04) include larger bog pools (C1.46) and a marginal lagg (C1.47), as well as the main mire surface (D1.1), which in actively-growing raised bogs typically comprises a complex of low hummocks, small pools and their associated vegetation. Raised bogs form only in cool climates with high rainfall. They are most widespread in the boreal zone and in the mountains and hills of the nemoral zone; they occur locally in the lowlands of the nemoral zone. They are characteristic of lowlands and hills of northwestern and northern Europe, the adjacent Hercynian ranges, the Jura, the Alps and the Carpathians. Bogs harbour, in addition to sphagna, which are often abundant, a small number of vascular plants such as Eriophorum vaginatum, Scirpus cespitosus (Trichophorum cespitosum), Carex pauciflora, Carex paupercula, Ledum palustre, Vaccinium oxycoccos, Andromeda polifolia and Drosera rotundifolia, and lichens. Animal species are not numerous but those that are adapted to bogs are highly specialised. Among typical invertebrates figure dragonflies (Leucorrhinia dubia, Aeshna subarctica, Aeshna caerulea, Aeshna juncea, Somatochlora arctica, Somatochlora alpestris), lepidopterans (Colias palaeno, Boloria aquilonaris, Coenonympha tullia, Vacciniina optilete, Hypenodes turfosalis, Eugraphe subrosea), beetles, ants (Formica exsecta), bugs and spiders (Pardosa sphagnicola, Glyphesis cottonae). Most of the species that bogs harbour are rare and their populations fragmented into isolated relictual elements; several are threatened. The remaining intact or nearly intact communities are exceptional.